In U.S. Pat. Nos. 3,902,972 and 4,405,340, there is described a reactor for gasifying solid granular fuels having particle sizes in the range from about 2 to about 80 mm under a pressure of 5 to 150 bars by a treatment with gasifying agents containing oxygen, water vapor and/or carbon dioxide.
The fuels constitute in the reactor a fixed bed, which descends slowly and into which the gasifying agents are introduced from below and from the lower end of which the incombustible mineral constituents of the fuels are withdrawn as solid ash or liquid slag.
The reactor comprises a rotary distributor, which is disposed above the fixed bed and has at least one fuel outlet structure that is directed toward the fixed bed. A lock chamber, which is disposed above the distributor, serves to deliver fuel to the distributor.
The gasification of solid fuels, particularly of hard coal or brown coal (lignite), is known and has been described, e.g. in Ullmanns Enzyklopadie der technischen Chemie, 4th edition (1977), on pages 383 to 386 of volume 14.
Details of a gasifying process involving solid ash are given in U.S. Pat. Nos. 3,540,967 and 3,854,895.
The process involving a withdrawal of liquid slag has been explained in British patent specifications Nos. 1,507,905; 1,508,671; and 1,512,677.
German patent specification No. 2,352,900 and published German application No. 30 32 949 and the corresponding U.S. Pat. Nos. 3,902,872 and 4,405,340, respectively, as noted above describe the gasification reactors provided with fuel distributors of the kind described hereinbefore.
These distributors have fuel discharge ducts having a leading portion (in the direction of displacement) which is disposed slightly below the trailing portion. In such an arrangement the leading portion of the duct may plow through the fuel that has been deposited on the fixed bed and may push some of the fuel aside if the descent of the fixed bed has been interrupted by some disturbance.
If the descent of the fixed bed of fuel has been interrupted by such disturbance and the fuel is pushed aside as described hereinbefore, new fuel can continuously flow onto the fixed bed so that the reactor will be charged with undesirably large quantities of fresh fuel in spite of the prolonged interruption of the gasification process.